When you're roleplaying use long sentences with as many descriptive words as you can. Use an online dictionary if you need to. Make sure your grammar is correct and you use punctuation when necessary.

When you write dialogue it should look like this:"Sure, just let me know when," said [name].

If you are writing with an action:"Of course I don't hate you." He turns around and faces her.

Make sure you have a full character. Make something along these lines:Name:Nickname:Age:Species:Race:Ethnicity:Family:Past:Background:Look:Quirks:Personality:

You also are going to want to be able to write out how they will react to a certain action. If you can't do this then you are going to want to think and write some ideas down for your character's personality.